The iris is a membranous ocular structure, situated at the rear of the cornea and and in the front of the crystalline lens, it defines and surrounds the pupillary opening whose diameter can change thanks to the movements of the iris. It has the shape of a circular disc and diaphragm acts as a diaphragm allowing light to enter the inner part of the eye. The main function of the iris is adjusting the amount of light that strikes the retina, both to protect the retina and to improve vision since, as in conditions of strong brightness, the restriction of the pupil ensures increased depth of focus expressed in dioptries and reduction of aberrations.
The pupil contraction is achieved through the sphincter muscle of the pupil, which surrounds the the pupil hedge (miosis); while through the dilator muscle of the pupil, radially arranged, it takes the dilation thereof (mydriasis).
The iris is pigmented, varying in color. The most common colors range from dark brown to light brown, more frequent in the Southern Caucasians, Asians and Negroids; fairly widespread, especially among Caucasian populations, are dark green tending to brown shades; then there are shades of gray, blue, blue and green light, mostly frequent in Northern Caucasians.
The biological function of the iris is very important, in fact, excessive exposure to sunlight can contribute to the development of cataracts or macular degeneration. Subjects with insufficient pigmentation are more sensitive to glare and predisposed to some eye diseases.
The coloration of the iris depends on the amount of melanin present. A greater amount of pigment in the iris of the eye yields a darker coloration, greater level of protection from ultraviolet radiation, and lower sensitivity to bright light.
In addition to the specific task to control the quantity of light that penetrates in the eye, by adjusting the amplitude of the pupil based on the brightness of the surrounding environment, to the iris is universally recognized an aesthetic function.
Thanks to the evoluting technologies applied to the production of contact lenses, it is now possible to temporarily change the eye color by using contact lenses, suitably pigmented with colors and designs different from the below iris. The cosmetic contact lenses should be regularly removed and, however, they can still provide risks and problems such as infections of the anterior segment of the eye, inflammatory reactions to the bulbar and tarsal conjunctiva, intolerance to the materials they are constituted of, or to the liquid solution wherein they are maintained, resulting in alterations of the cornea and relative decrease of visual acuity. Contact lenses also can be worn by many individuals, including people with dry eye syndrome or chronic diseases of the corneal surface and the conjunctiva.
Refractive surgical techniques providing for the introduction of inserts in the corneal stroma in order to correct visual defects such as myopia, hyperopia and astigmatism, or corneal insert restricting the pupillary aperture in order to allow a better near vision, have shown good tolerability without drawbacks. Hence, also the modern eye cosmetology has adapted and proposed artificial iris implants, widely used in classic ophthalmics to control glare and photophobia caused by iris defects, congenital or post-traumatic, complete (aniridia) or partial (colobomas), as implants developed to change eye color.
The U.S. Pat. No. 7,722,669 relates to a method for changing eye color comprising forming a coplanar annular channel around the pupil in the corneal stroma, by means of laser or surgical techniques, extending from the pupillary hedge up toward the limbus. The method provides that a biocompatible material, at least partially opacified, is inserted into the channel. The biocompatible material according to the invention is a dispersion of particles comprising an opacified material, permeable to be injected, hence in the form of liquid or hydrogel. Alternatively, the biocompatible material may include a thin layer of polymeric material, as a slurry comprising an opacified material.
This mash gives a homogeneous and opaque color quite far from iris natural aesthetic iris.
Although the subject-matter described in U.S. Pat. No. 7,722,669 is a permanent or semi-permanent method, to change the color of the eye which provides several benefits over the corneal contact lenses method, however, it does not totally solve some problems related to the particular conformation of the annular channel wherein the biocompatible material is inserted to give the new color. The realization of a intrastromal channel to be filled with a gelatinous colored mass, implies the occurrence of tensions on the corneal structure that, above certain thickness, can vary the curvature in its central portion, or areas involved in vision. However, the method of such US patent does not provide a technique able of ensuring the uniformity of layer thickness, of the order of 3-5 microns. Such uniformity, if not maintained, can generate different forces causing the occurrence of irregular astigmatisms, which, although minor, definitely interfere with the quality of vision. A further disadvantage is that to restore the transparency of the cornea the gelatinous slurry has to be aspirated from the tunnel in which it was placed. Therefore, needle cannulae, connected to vacuum systems or irrigation—suction, more or less simple, which through various incisions have to enter the route of the tunnel, with the consequent invasiveness on the corneal tissues should be used.
The US patent application 2012/0143325 describes corneal inlays and methods of improving vision of a patient by using said corneal inlays. Said application is directed to corneal inlays designed as intrastromal corneal inserts constituted by a film of solid transparent, impermeable, biocompatible, physiologically inert, and chemically resistant material, designed to receive any type of print, configured to position an opening within optical path of the eye for compensating for for inadequate optical performance of the eye, such as presbyopia, increasing the depth of focus of the patient. The invention described in US 2012/0143325, as most optical devices designed for capsular bag implantation, is preferably constituted of polyvinylidene fluoride (PVDF). PVDF has desirable characteristics to be used in ocular inlays such as being relatively chemically inert and having a relatively high UV resistance. Furthermore, according to said invention, PVDF can be made opaque by opacification agents providing sufficient opacity to produce the sought depth of field improvements. According to US 2012/0143325 the insertion of the implant affect the pupillary region because it has to magnify the vision; the inlays extend from the inner periphery at a radial distance of 0.8 mm to the outer periphery at a radial distance of 1.9 mm. In general, the thickness of the inlay is within the range of from about 1 to about 40 micron, and often in the range from about 5 to about 20 micron. In preferred embodiments the thicknesses is about 5 or 10 micron. Of course, considering the aim of the ocular device and moreover the site of insertion, the selection of the thickness range values of any corneal inlay cannot deviate from that representation.
For applying the corneal inlay to the eye of a patient according to US 2012/0143325 various techniques may be employed to position the device at different depths or between different layers within the cornea. In particular a corneal flap of suitable depth is hinged open. The depth of the flap varies between about the outermost 20% and about the outermost 5% of the thickness of the cornea.
The US patent application 2012/0245683 describes a corneal implant adapted for implantation between layers of the cornea to focus an image on a retina of an eye including an inlay, an outer perimeter, and a clear central region capable of refracting light to compensate for a refractive error of an eye. The inlay also has an annular opaque region comprising a plurality of holes. The annular opaque region extends from the outer circumference of the inlay to the clear central portion. The opaque region extends over a minority of the surface area of the implant. According to the invention, the holes dispersed about the device in the non-transmissive region, have a double function, in fact, they have a configuration to provide an adequate amount of gripping or position holding capability. Once the ocular device is implanted in the stromal layer of the cornea, corneal tissue adjacent to the recesses swells or expands into the recesses. By permitting corneal tissue to expand into the recesses, the likelihood of the ocular device becoming displaced within the cornea after being implanted or to otherwise moving relative to the eye can be reduced. In some cases, the expansion of the corneal tissue into the recesses is due to osmotic pressure or an effect similar to a capillary effect. Furthermore, the holes preferably are also configured to maintain the transport of one or more nutrients across the device. Preferably, the holes provide sufficient flow of one or more nutrients across the device to prevent depletion of nutrients in the first corneal layer adjacent the anterior surface of the device. For example, in certain embodiments, the holes provide sufficient flow of glucose across the device between the corneal tissue layers adjacent the device to prevent glucose depletion that would harm the adjacent corneal tissue.
However, the technical solutions proposed by documents US 2012/0143325 and US 2012/0245683 aimed to compensate refractive error and loss of accommodation do not solve at all the technical problem of providing an corneal intrastromal insert configurated to change the color and appearance of the eye, improving the ability to absorb radiation, normalizing the function of the iris, whenever anatomically compromised, and the method for insertion thereof within the cornea of the eye.
Therefore, it is strongly felt the need to have alternative methods to change the color of the eye, to normalize any structural abnormalities of the iris and to provide means of absorption of the electromagnetic radiation which do not present the disadvantages of the methods of the state of the art, while still ensuring the reversibility.